Wireless networks have experienced increased development in the past decade. One of the most rapidly developing areas is mobile ad-hoc networks (MANETs). Physically, a MANET includes a number of geographically-distributed, potentially mobile nodes sharing a common radio channel. Compared with other types of networks, such as cellular networks or satellite networks, the most distinctive feature of MANETs is the lack of any fixed infrastructure. The network may be formed of mobile nodes only, and a network is created “on the fly” as the nodes transmit or come within range of each other. The network does not depend on a particular node and dynamically adjusts as some nodes join or others leave the network.
Because of these unique characteristics, routing protocols for governing data flow within MANETs are required which can adapt to frequent topology changes. Two basic categories of MANET routing protocols have emerged in recent years, namely reactive or “on-demand” protocols, and proactive or table-driven protocols. Reactive protocols collect routing information when a particular route is required to a destination in response to a route request. Examples of reactive protocols include ad-hoc on demand distance vector (AODV) routing, dynamic source routing (DSR), and the temporally ordered routing algorithm (TORA).
On the other hand, proactive routing protocols attempt to maintain consistent, up-to-date routing information from each node to every other node in the network. Such protocols typically require each node to maintain one or more tables to store routing information, and they respond to changes in network topology by propagating updates throughout the network to maintain a consistent view of the network. Examples of such proactive routing protocols include destination-sequenced distance-vector (DSDV) routing, which is disclosed in U.S. Pat. No. 5,412,654 to Perkins; the wireless routing protocol (WRP); and clusterhead gateway switch routing (CGSR). A hybrid protocol which uses both proactive and reactive approaches is the zone routing protocol (ZRP), which is disclosed in U.S. Pat. No. 6,304,556 to Haas.
Despite utilizing different approaches to discovering the available data routes between a source node and a destination node in a MANET, one common feature most MANET protocols share is the fact that they typically select a single, designated route from among the available routes over which the source and destination nodes then communicate. The selection of this designated route is typically based upon one or more quality of service (QoS) factors, such as the available bandwidth, delay, etc. associated with the route.
Of the many challenges of transmitting data in the dynamic MANET environment, reliability of the wireless communications links which form the routes between network nodes may be particularly problematic. One device which attempts to address link reliability problems is the NovaRoam Series 250 and 350 Wireless Routers from Nova Engineering, Inc., of Cincinnati, Ohio, which implements forward error correction (FEC) techniques to enhance communication link reliability. These routers apply FEC at the physical network layer, as is done in most conventional communications systems and networks. The FEC operates only over a single hop, that is, the decoding is done after each hop after receiving the transmission. Then, if another hop along a route is needed, the information is again encoded and again decoded upon reception by the next node.
While such devices may provide some level of improvement, they still may not provide sufficient error correction when certain events occur. For example, such events may include dropouts due to handover problems or even the loss of a route.